I doubt that small amount will be detectable in a 5 gallon batch, even without cold crashing and decanting.
As
@Jag75 said, if you're cold crashing and decanting, chances are whatever off-flavor it produced, most of it will be tossed out with the starter beer upon decanting. That should give you peace of mind.
Just on process, why not boil the starter wort in a stainless cooking pot (must be clean), that has a matching, well fitting lid? You can much easier stir it, preventing scorching.
When placed in a sink or dishwash tub with cold water it will chill much faster than in a flask, and you won't be afraid of your flask cracking on the stove due to uneven heating. When cooled to pitching temps, pour into your sanitized flask through a sanitized funnel. Then pitch the yeast. I've made 100s of starters that way, never had a flask failure or scorched wort.
Just make sure you use good sanitation during the process, and nothing can get in your starter wort by splashing etc. Wipe the (pouring) edge with Starsan or rubbing alcohol before pouring, etc.